1ST-TRIMESTER MATERNAL SERUM SCHWANGERSCHAFTS PROTEIN-1 (SP1) IN PREGNANCIES ASSOCIATED WITH CHROMOSOMAL-ANOMALIES

The relationship between first-trimester maternal serum Schwangerschaf ts protein 1 (SP1) and the karyotype of the pregnancy was examined in 692 women who underwent chorionic villus biopsy at 6-12 weeks. There w ere 30 pregnancies with abnormal karyotypes, consisting of 14 Down's s yndrome (DS), eight trisomy 18, and eight other anomalies, two of whic h were mosaics. The normal ranges and medians for gestation were defin ed from the 662 cases in which the karyotype was normal. The median SP 1 (0.5 MOM) of the abnormal group was significantly lower than that of the normal group (1.0 MOM). This relationship was maintained for the DS pregnancies (0.4 MOM) and for anomalies other than trisomy 18 (0.43 MOM) but not trisomy 18 (1.1 MOM). It is possible that the use of SP1 as a screening test for chromosome anomalies in the first trimester c ould have a 43 per cent detection rate for a 5 per cent false-positive rate.